Suspension bridge extension structure and method for transversely adding main cables to form four spatial main cables

Abstract

The invention discloses a suspension bridge extension structure and method for transversely adding main cables to form four spatial main cables, and belongs to the technical field of civil engineering bridges, the suspension bridge extension structure comprises existing stiffening beams, widening extension parts of the existing stiffening beams are connected to the newly added main cables through newly added slings, and the newly added main cables are arranged on the sides, far away from the center line of a bridge axis, of the existing main cables; the distance between the center of the newly-added main cable and the center line of the bridge shaft is gradually increased from the tower top to the midspan, and the transverse distance between the midspan and the center line of the bridge shaft is maximum; the newly-added slings corresponding to the newly-added main cable and the existing slings of the existing main cable are longitudinally arranged at intervals. The method comprises the following steps: expanding the cross section of an existing bridge tower, adding an anchorage foundation, relying on the existing bridge tower and an existing main cable, and erecting a newly added main cable; the stiffening beams are widened on the two sides of the existing stiffening beams, and the newly-added and expanded stiffening beams on the two sides are supported through newly-added space main cables; the existing suspension bridge body structure can be utilized, land is effectively saved, and real expansion is achieved. The hybrid four-main cable improves the system damping, and the dynamic stability of the extension structure is good.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering bridges, and particularly relates to an expansion structure of a suspension bridge with four main cables formed by newly adding main cables horizontally to form a spatial four-main-cable structure. Background Technique

[0002] The statements in this part merely provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] With the development of productivity, the per capita vehicle ownership has been continuously increasing. The traffic volume of some early-built roads is becoming saturated day by day, and it is urgent to improve the traffic capacity, quality, efficiency and save resources through reconstruction and expansion. Among them, bridges are the key and difficult points in reconstruction and expansion, especially large bridges such as suspension bridges.

[0004] The existing suspension bridge widening technology usually adjusts the deck layout and increases the traffic lane or sidewalk while keeping the weight of the deck system unchanged. However, since the main cable of the load-bearing structure cannot be increased, the width of the deck that can be increased by the existing widening is extremely limited, and real expansion cannot be achieved. For suspension bridges with expansion requirements, in engineering practice, it is mostly achieved by building a new suspension bridge beside the existing suspension bridge. However, the connection of the route and interchange between the new project and the bilateral widening of the existing road has a large influence range, the smoothness of the engineering route is average, the investment is large and the construction occupation space is large. And in some areas, due to restrictions on waterways and flood control, it is impossible to build a new bridge beside the existing suspension bridge.

[0005] The prior art also discloses a widening structure of a suspension bridge with four main cables vertically arranged. The newly added main cable is vertically stacked with the existing main cable, and the anchorage of the newly added suspender and the existing suspender is at the same position, resulting in a dense arrangement of anchorage steel plates at this place, large welding residual stress of the anchorage steel plates, and bearing dynamic loads, thus resulting in large fatigue stress at this place, and it is easy to have problems of structural damage and fatigue failure; the distance between the newly added suspender and the existing suspender is small, and the suspenders are prone to large deformation and collision under the action of strong wind, which is not conducive to the durability of the bridge. Summary of the Invention

[0006] In view of the above problems, the present invention provides a suspension bridge expansion structure and method for horizontally adding main cables to form a spatial four-main-cable structure. The upper anchor points of the sling beams of the newly added spatial main cables are located on the transverse outer side (away from the bridge axis center line side) of the widened part of the stiffening girder. At the same time, the newly added slings and the existing slings are arranged at intervals in the bridge length direction (longitudinal direction), so that the longitudinal and transverse positions of the upper anchorage points of the newly added slings and the existing slings on the girder are different, avoiding the concentrated arrangement of the anchorage steel plates on the stiffening girder and preventing problems such as structural damage and fatigue failure caused by large welding residual stress and fatigue stress of the anchorage steel plates; the characteristic of the longitudinal interval arrangement of the newly added slings and the existing slings, that is, the distance between the newly added slings and the existing slings is large, avoiding the collision problem between the slings under the action of strong wind; the newly added main cables and the existing main cables are arranged side by side at the top of the tower, located on the side of the existing main cables far from the bridge axis center line. The distance from the lowest point at the mid-span of the newly added main cable to the bridge axis center line is greater than that of the tower vertex. That is, the newly added main cable on the outside is a spatial cable, and the existing main cable in the middle is a planar cable, forming a spatial four-main-cable structure, increasing the system damping and improving the dynamic stability of the suspension bridge.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In the first aspect, a suspension bridge expansion structure for horizontally adding main cables to form a spatial four-main-cable structure is provided, which is built based on an existing suspension bridge. The existing suspension bridge includes an existing stiffening girder, existing main cables, existing slings, existing main saddle, existing bridge towers, existing anchor foundation, existing cable saddles and anchoring systems; existing bridge towers are provided at both ends of the mid-span of the existing stiffening girder. The existing main cables are supported on the existing bridge towers through the existing main saddle and are anchored on the existing anchor foundations on both sides of the bridge towers through the existing cable saddles and anchoring systems; along the bridge length direction, widened parts are newly added to both sides of the existing stiffening girder in the transverse direction and are connected into a whole; the widened parts on both sides of the stiffening girder are connected to the newly added main cables through the newly added slings, and the newly added main cables are arranged outside the existing main cables; they are supported on the expanded bridge towers through the newly added main saddle and are anchored on the newly added anchor foundations through the newly added cable saddles and anchoring systems;

[0009] The distance from the center of the newly added main cable to the bridge axis gradually increases from the top of the tower to the mid-span, and the transverse distance from the mid-span to the bridge axis is the largest. That is, the newly added main cable forms a certain angle with the vertical plane and is a spatial main cable; the corresponding transverse distance from the upper anchor point of the newly added sling beam to the bridge axis center line is fixed, and the distance from the upper anchor point on the cable to the bridge axis center line gradually increases from the top of the tower to the mid-span, which is an inclined sling; the newly added inclined slings and the existing vertical slings are arranged at intervals longitudinally.

[0010] Preferably, the newly added main saddle and the existing main saddle are arranged side by side at the top of the tower, and the newly added main saddle is located on the transverse outer side of the existing main saddle; the elevation of the newly added main cable and the existing main cable at the top of the tower is the same.

[0011] Preferably, the mid-span elevation of the newly added main cables is higher than that of the existing main cables by a set distance; the two newly added main cables or the two existing main cables are arranged symmetrically with respect to the bridge axis horizontally.

[0012] Preferably, the bridge tower is divided into an existing bridge tower and an expanded cross-section of the bridge tower. The expanded cross-section of the bridge tower is arranged on the longitudinal and lateral outsides of the existing bridge tower. The existing main saddle is arranged on the top surface of the existing bridge tower, at the horizontal center of the cross-section of the top of the existing bridge tower; the newly added main saddle is arranged on the top surface of the expanded bridge tower, outside the existing main saddle horizontally.

[0013] Preferably, the center distance between the saddle grooves of the newly added main saddle and the existing main saddle is controlled according to twice the diameter of the newly added main cable. The saddle groove shape of the newly added main saddle is arranged at an oblique angle with respect to the vertical plane, which is the same as the oblique angle of the mid-span of the newly added main cable with respect to the vertical plane.

[0014] Preferably, on both sides of the side spans of the existing suspension bridge, two existing anchor foundation bases are respectively arranged. An existing cable saddle and an anchoring system are arranged on the existing anchor foundation bases. The two ends of the two existing main cables are respectively connected to the existing cable saddle and the anchoring system; a newly added cable saddle and an anchoring system, and a newly added anchor foundation base are also arranged for anchoring the two ends of the newly added main cables.

[0015] Preferably, the newly added anchor foundation base and the existing anchor foundation base are arranged separated front and back, and the newly added anchor foundation base is adapted to the inclination angle of the newly added main cable. At the same time, it avoids the connection structures of the side spans of the suspension bridge and is arranged on the lateral outside of the existing anchor foundation base.

[0016] Preferably, the existing stiffening girder can adopt a box girder, a truss girder or a plate girder. The widened and expanded parts on both sides of the stiffening girder are connected to the existing stiffening girder by welding or bolts; anchoring devices are arranged on the lateral outsides of the widened and expanded parts on both sides of the stiffening girder. One end of the newly added suspender is connected to the cable clamp of the newly added main cable, and the other end is connected to the anchoring device.

[0017] In the second aspect, an expansion method for the expansion structure of the suspension bridge with four main cables formed by horizontally adding the above-mentioned main cables is provided, including the following steps:

[0018] S1. New bored cast-in-place pile foundations and new bearing platforms are added on the lateral outside of the existing bridge tower foundation; the new bearing platform and the existing bearing platform are formed into a whole by implanting steel bars;

[0019] S2. On the basis of the new bearing platform, the cross-section of the existing bridge tower is expanded, and the expanded part and the existing part are connected into a whole by means of implanting steel bars, etc.; after the expansion of the bridge tower is completed, a newly added main saddle is installed outside the existing main saddle at the top of the tower;

[0020] S3. Pour the newly added anchor foundation base and set the newly added cable saddle and the anchoring system;

[0021] S4. Relying on the expanded bridge towers and the existing main cables, install the catwalk for the new main cables and erect the new main cables. After the erection is completed, the mid-span of the new main cables will appear as a flat main cable under the action of their own weight.

[0022] S5. Use multiple cross braces between the mid-spans of the two newly added main cables, and gradually add sections and push them up to expand the mid-spans of the two newly added main cables to achieve the spatial cable state after the bridge is widened; install the new slings according to the set distance, and the new slings are not tensioned at this time;

[0023] S6. The widened and expanded parts on both sides of the stiffening beam are divided into longitudinal sections and hoisted and installed in place by a separate self-propelled cable-carrying crane supported on the newly added main cable until the middle span is closed; temporary connections are used between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and between the beam sections of the existing stiffening beams;

[0024] S7. Slightly adjust the elevation of the interface between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and the existing stiffening beam sections, as well as the cable force of the newly added slings, and then adjust the temporary connection between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and the existing stiffening beam sections to a permanent connection by welding or high-strength bolts; then remove the cross brace and the temporary brackets used for transporting and installing the beam sections of the widened and expanded parts on both sides of the stiffening beam;

[0025] S8. Wrap the newly added main cable with wire for protection; then dismantle the catwalk; complete the sealing project of the newly added loose cable saddle and anchoring system and the newly added main cable saddle; finally, carry out acceptance and open to traffic operation.

[0026] Preferably, in S6, the beam transport machinery transports the widened and expanded beam sections on both sides of the stiffening beam from the existing stiffening beam bridge deck to their locations; after the widened and expanded beam sections on both sides of the stiffening beam are installed in place, the newly added slings corresponding to the widened and expanded beam sections on both sides of the stiffening beam are tensioned.

[0027] Compared with the prior art, the present invention has the following advantages and positive effects:

[0028] Compared with the prior art, the upper anchor point of the sling beam of the newly added spatial main cable of the present invention is located laterally outside the extended part of the stiffening girder (away from the bridge axis center line side). At the same time, the newly added slings and the existing slings are arranged at intervals in the bridge length direction (longitudinal direction), so that the longitudinal and lateral positions of the upper anchorage points of the newly added slings and the existing slings on the beam are different, avoiding the concentrated arrangement of the anchorage steel plates on the stiffening girder and avoiding the problems of structural damage and fatigue failure caused by the large welding residual stress and fatigue stress of the anchorage steel plates; the characteristic of the longitudinal interval arrangement of the newly added slings and the existing slings, that is, the distance between the newly added slings and the existing slings is large, avoiding the collision problem between the slings under the action of strong wind; the newly added main cable and the existing main cable are arranged side by side at the top of the tower, located on the side of the existing main cable far from the bridge axis center line. The distance from the lowest point at the mid-span of the newly added main cable to the bridge axis center line is greater than the tower vertex. That is, the newly added main cable on the outside is a spatial cable, and together with the existing planar main cable in the middle, it forms a spatial four-main cable system, increasing the system damping and improving the dynamic stability of the suspension bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0030] Figure 1 is the front view of the suspension bridge expansion structure of Embodiment 1 or 2 of the present invention;

[0031] Figure 2 is the side view at the bridge tower of the suspension bridge expansion structure of Embodiment 1 or 2 of the present invention;

[0032] Figure 3 is the side view of the expanded part and the existing part of the top surface of the bridge tower and the main cable saddle of Embodiment 1 or 2 of the present invention;

[0033] Figure 4 is the front view of the widened stiffening girder supported by the existing slings of Embodiment 1 or 2 of the present invention;

[0034] Figure 5 is the front view of the widened stiffening girder supported by the newly added slings of Embodiment 1 or 2 of the present invention;

[0035] Figure 6 is the top view of the existing suspension bridge of Embodiment 1 or 2 of the present invention after the addition of new anchor piers and the expansion of the bridge tower;

[0036] Figure 7 is the top view of the existing suspension bridge of Embodiment 1 or 2 of the present invention under the self-weight action after the erection of the newly added main cable;

[0037] Figure 8 is the top view of the existing suspension bridge of Embodiment 1 or 2 of the present invention after the addition of cross braces between the newly added two main cables to form a spatial cable shape;

[0038] Figure 9 It is a top view of the process of expanding an existing suspension bridge in Embodiment 1 or 2 of the present invention. The expansion is carried out by using a cable-suspended crane on the newly added main cable to suspend cables from the bridge tower to the mid-span and erect the widened parts on both sides of the stiffening girder.

[0039] Figure 10 It is a top view of the process of expanding an existing suspension bridge in Embodiment 1 or 2 of the present invention until the closure of the widened parts on both sides of the stiffening girder is achieved by using a cable-suspended crane on the newly added main cable to suspend cables from the bridge tower to the mid-span and erect the widened parts on both sides of the stiffening girder.

[0040] Figure 11 It is a top view of the completed state of the bridge after the widening and expansion of both sides of the stiffening girder of the existing suspension bridge in Embodiment 1 or 2 of the present invention.

[0041] Figure 12 It is a 1 / 2 three-dimensional view of the suspension bridge expansion structure in Embodiment 1 or 2 of the present invention.

[0042] In the figure:

[0043] 1. Newly added main cable; 2. Existing main cable; 3. Newly added suspender; 4. Existing suspender; 5. Existing stiffening girder; 6. Widened and expanded parts on both sides of the stiffening girder; 7. Existing bridge tower; 8. Newly added cross-section of the bridge tower expansion; 9. Existing main saddle; 10. Newly added main saddle; 11. Tower-girder connection device; 12. Existing saddle and anchorage system; 13. Existing anchor foundation; 14. Newly added saddle and anchorage system; 15. Newly added anchor foundation. Detailed implementation manners

[0044] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0045] The following will describe the present invention in detail with reference to the accompanying drawings. The suspension bridge expansion structure with a spatially four-main-cable formed by horizontally adding a new main cable disclosed in this embodiment is constructed based on an existing suspension bridge. As shown in Figure 1 , Figure 11 , the structure of the existing suspension bridge before expansion consists of an existing stiffening girder 5, existing suspenders 4, existing main cables 2, existing main saddles 9, existing bridge towers 7, existing anchor foundations 13, and existing saddle and anchorage systems 12. Among them, the existing stiffening girder 5 at the existing bridge tower 7 is vertically supported by a tower-girder connection device (usually a bearing) supported on the existing bridge tower 7, thereby transferring part of the load of the existing stiffening girder at both ends of the suspension bridge to the existing bridge tower 7. Before expansion, the existing suspension bridge is generally a two-tower single-span two-hinged steel girder suspension bridge.

[0046] Specifically, along the length direction of the existing suspension bridge, widened and extended parts 6 are added on both sides of the new stiffening girders on both sides of the existing stiffening girder 5 and connected into a whole to increase the deck width, thereby increasing the traffic lanes; the widened and extended parts 6 on both sides of the stiffening girder can be connected to the existing stiffening girder 5 by welding or bolts; the widened and extended parts 6 on both sides of the stiffening girder are connected to the new main cable 1 through newly added suspenders 3, and the new main cable 1 is arranged laterally outside the existing main cable 2 (laterally outside means the side far from the bridge axis center line); the dead load and operating live load of the widened and extended parts 6 on both sides of the stiffening girder are borne by the new main cable 1. Bridge decks are provided on both the widened and extended parts 6 on both sides of the stiffening girder and the existing stiffening girder 5.

[0047] As Figure 1 , Figure 2 , Figure 3 shown, bridge towers are provided at both ends of the mid-span of the existing stiffening girder 5 of the suspension bridge. The bridge towers are divided into the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower extension; a main cable saddle is provided at the top of the bridge tower. The main cable saddle includes the newly added main cable saddle 10 and the existing main cable saddle 9. The new main cable 1 is installed on the newly added main cable saddle 10, and the existing main cable 2 is installed on the existing main cable saddle 9; the newly added main cable saddle 10 corresponding to the new main cable 1 and the existing main cable saddle 9 corresponding to the existing main cable 2 are arranged side by side. The lateral distance from the center of the new main cable 1 to the bridge axis center line gradually increases from the top of the tower to the mid-span, and the lateral distance at the mid-span point from the bridge axis is the largest; the lateral distance between the mid-span point of the new main cable 1 and the bridge axis center line is greater than the lateral distance between the tower top point and the bridge axis center line, that is, the new main cable 1 forms a certain angle with the vertical plane. The inclination angle between the new main cable 1 and the vertical plane is determined by the coordinates at the mid-span of the new main cable 1.

[0048] It can be understood that there are two existing bridge towers 7, which are respectively arranged at both ends of the mid-span of the existing stiffening girder 5 of the suspension bridge. It can also be understood that before the expansion, the weight of the beam segment and the operating live load at the intersection part of the existing bridge tower 7 and the existing stiffening girder 5 are transmitted to the existing bridge tower 7 through the tower-beam connection device 11 (generally a bracket support, arranged on the relatively inner side of the existing bridge tower); after the expansion, the weight of the beam segment and the operating live load at the intersection part of the expanded bridge tower (including the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower extension) with the existing stiffening girder 5 and the widened and extended parts 6 on both sides of the stiffening girder are transmitted to the expanded bridge tower (that is, the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower extension) through the strengthened tower-beam connection device 11 (that is, the bracket support is also expanded and newly added).

[0049] It should be noted that the elevation of the top of the newly added main cables 1 on both sides is the same as that of the existing main cables 2 at the tower top, and the newly added main cables 1 have a certain inclination angle with the vertical plane; in order to achieve the spatial cable shape of the newly added main cables 1 after the completion of the bridge, it is necessary to set up a cross brace in the middle of the newly added main cables 1 that are in a vertical state under their own weight and located on the left and right sides in the transverse direction of the bridge for jacking. During the erection of the cross brace and the jacking process, in order to avoid the interference between the cross brace and the corresponding construction technology and the existing main cables 2, the mid-span of the newly added main cables 1 is to be higher than the mid-span of the existing main cables 2 by a set distance; in this embodiment, this set distance is at least 5.0 m at minimum. The two newly added main cables 1 and the two existing main cables 2 are arranged symmetrically in the transverse direction with respect to the bridge axis center line.

[0050] As Figure 2 , Figure 3 shown, the newly added main saddle 10 and the existing main saddle 9 are arranged side by side, and the vertical loads transmitted by the newly added main cables 1 and the existing main cables 2 are transmitted to the overall cross-section composed of the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower extension through the newly added main saddle 10 and the existing main saddle 9; specifically, the newly added cross-section 8 of the bridge tower is arranged on the longitudinal and transverse outer sides of the existing bridge tower 7, and the newly added cross-section 8 of the bridge tower is used to increase the cross-sectional size of the existing bridge tower 7, thereby improving the compressive and flexural compressive bearing capacity of the bridge tower, so as to provide vertical support for the newly added main cables 1.

[0051] The saddle groove center distance between the newly added main saddle 10 and the existing main saddle 9 is controlled according to twice the diameter of the newly added main cable 1 to ensure the construction space during the cable forming process of the newly added main cable 1; the saddle groove shape of the newly added main saddle 10 corresponding to the newly added main cable 1 is arranged obliquely, and the oblique inclination angle of the saddle groove axis of the newly added main saddle 10 with the vertical plane is the same as the oblique inclination angle of the space plane where the newly added main cable 1 is located with the vertical plane.

[0052] As Figure 2 shown, the newly added cross-section 8 of the bridge tower needs to first expand the foundation of the existing bridge tower 7. Specifically, new bored pile foundations are added on the longitudinal and transverse outer sides of the foundation of the existing bridge tower 7, and a new bearing platform is poured on the top of the newly added bored piles; the new bearing platform and the bearing platform of the existing bridge tower foundation are integrated by implanting steel bars in the bearing platform of the existing bridge tower foundation and pouring; on the basis of the new bearing platform, the tower column cross-section of the existing bridge tower 7 is expanded laterally outward to form an expanded bridge tower formed by the combination of the newly added cross-section 8 of the bridge tower and the existing bridge tower 7; the cross-sections of the newly added cross-section 8 of the bridge tower and the existing bridge tower 7 are connected into an integral whole. If the existing bridge tower 7 is made of concrete, steel bars are implanted in the existing concrete bridge tower and then connected into an integral whole; if the existing bridge tower 7 is made of steel, it is connected to the existing steel structure bridge tower through welding and high-strength bolts to form an integral whole.

[0053] After the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower are connected into an integral whole, the newly added main saddle 10 is installed on the transverse outer side of the existing main saddle 9 at the top of the extension to support the newly added main cable 1 and smoothly change the cable shape of the newly added main cable 1.

[0054] On both sides of the side span of the existing suspension bridge, there are respectively an anchor foundation, a cable saddle and an anchoring system. Specifically, there are two existing anchor foundations 13 on both sides of the side span of the existing suspension bridge, and an existing cable saddle and an anchoring system 12 are arranged on the existing anchor foundation 13. The two ends of the two existing main cables 2 are respectively connected to the existing cable saddle and the anchoring system 12 on both sides of the side span of the existing suspension bridge. On both sides of the side span of the existing suspension bridge, in order to support the newly added main cable 1, a newly added cable saddle and an anchoring system 14 and a newly added anchor foundation 15 are also arranged to anchor the two ends of the newly added main cable 1.

[0055] To avoid the newly added main cable 1, the newly added anchor foundation 15 and the newly added cable saddle and anchoring system 14 from affecting the driving space of the side span connection line after the expansion; the newly added anchor foundation 15 is adapted to the angle of the newly added main cable 1, and the newly added anchor foundation 15 needs to be arranged on the lateral outside of the highway structure of the side span after the expansion. To reduce the influence of the foundation pit excavation of the newly added anchor foundation 15 on the existing anchor foundation 13, the newly added anchor foundation 15 and the existing anchor foundation 13 are arranged separately before and after.

[0056] In some embodiments, the newly added anchor foundation 15 and the existing anchor foundation 13 can also be arranged side by side but at a certain distance; that is, the side span anchor points of the newly added main cable 1 and the side span anchor points of the existing main cable 2 have different coordinates. Correspondingly, the line type on the side span side of the newly added main cable 1 is different from the line type on the side span side of the existing main cable 2.

[0057] As Figure 1 shown, the newly added suspenders 3 corresponding to the newly added main cable 1 and the existing suspenders 4 of the existing main cable 2 are arranged longitudinally at intervals; that is, as Figure 4 、 Figure 5 shown, only one group of newly added suspenders 3 or existing suspenders 4 is arranged on the same cross-section of the existing stiffening girder 5 of the suspension bridge after the expansion and the widened and extended parts 6 on both sides of the stiffening girder, so as to suspend and support the existing stiffening girder 5 and the widened and extended parts 6 on both sides of the stiffening girder on the newly added main cable 1 or the existing main cable 2, so that the load borne by each group of suspenders is basically the same, and the cable force of the existing suspenders 4 after the expansion is controlled to be less than or equal to the cable force before the expansion; at the same time, for the newly added main cable 1 and the existing main cable 2, the weight transmitted by the stiffening girder and the suspenders borne by each main cable is the same.

[0058] The newly added main cable 1 is connected to the widened and extended parts 6 on both sides of the stiffening girder through the newly added suspenders 3, that is, the newly added suspenders 3 transmit the dead and live loads of the existing stiffening girder 5 of the beam segment where they are located and the widened and extended parts 6 on both sides of the stiffening girder to the newly added main cable 1. It should be noted that, as Figure 7 shown, after the newly added main cable 1 is erected, it only bears its own weight; that is, after the newly added main cable 1 is first formed; the middle span (the middle of the two existing bridge towers 7 is the middle span) is a planar main cable, and the distance from the mid-span to the top of the tower to the bridge axis is the same, and it is in the vertical plane.

[0059] AsFigure 11 As shown in the figure, after the expansion is completed, in the bridge operation state, the newly added main cable 1 presents a spatial cable shape, that is, the distance from the mid-span of the newly added main cable 1 to the center line of the bridge axis is greater than the distance from the top of the tower to the center line of the bridge axis. In the completed bridge state, the newly added main cable 1 presents a spatial cable shape because of the lateral pulling force of the newly added hanger 3, that is, the spatial cable shape of the newly added main cable 1 is formed by the self-weight of the main cable and the pulling force constraint of the newly added hanger 3. The newly added hanger 3 is inclined on the cross-section of the existing stiffening girder 5 and has a certain inclination angle with the vertical plane, that is, the distance from the cable clamp at the connection between the upper end of the newly added hanger 3 and the newly added main cable 1 to the center line of the bridge axis is less than the distance from the anchoring device at the connection between the lower end of the newly added hanger 3 and the widened and extended parts 6 on both sides of the stiffening girder to the center line of the bridge axis.

[0060] It should be explained that between the anchor head at the lower end of the newly added hanger 3 and the widened and extended parts 6 on both sides of the stiffening girder, an anchoring device such as an anchor head bearing type or a pin-connected type is used for connection; the anchor head bearing type or pin-connected type and other anchoring devices are integrally manufactured, installed and formed with the widened and extended parts 6 on both sides of the stiffening girder.

[0061] Such as Figure 4 , Figure 5 shown, the existing stiffening girder can adopt a box girder, a truss girder or a plate girder, and an anchoring device is arranged on the lateral outside of the widened and extended parts 6 on both sides of the stiffening girder. Such as Figure 1 , Figure 2 , Figure 5 shown, the upper end of the newly added hanger 3 is connected to the newly added main cable 1, and the lower end is connected to the widened and extended parts 6 on both sides of the stiffening girder through an anchoring device, that is, the widened and extended parts 6 on both sides of the stiffening girder are suspended and supported on the newly added main cable 1 through the newly added hanger 3; the newly added carriageway is separated from the existing carriageway by the existing anti-collision guardrail and the existing hanger.

[0062] Such as Figure 12 , the newly added main cable 1 forms a certain angle with the vertical plane and is a spatial cable; the two existing main cables 2 are located in the vertical plane, and the newly added main cable 1 and the existing main cables 2 together form a spatial four-main-cable structure.

[0063] Embodiment 2

[0064] The method for expanding the suspension bridge structure with a spatial four-main-cable structure formed by laterally adding a main cable provided in this embodiment uses the suspension bridge expansion structure with a spatial four-main-cable structure formed by laterally adding a main cable disclosed in Embodiment 1, and includes the following steps:

[0065] S1. Expand the foundation of the existing bridge tower 7: As Figure 2 , Figure 6 shown, bored cast-in-place pile foundations are newly added on the lateral outside of the foundation of the existing bridge tower 7; a new bearing platform is poured on the top of the newly added bored cast-in-place piles; the new bearing platform and the bearing platform of the existing bridge tower foundation are formed into a whole by implanting steel bars in the bearing platform of the existing bridge tower foundation and pouring.

[0066] S2. Expand the cross-section of the existing bridge tower 7: As Figure 2 , Figure 6 shown, on the basis of the newly added bearing platform in S1, expand the cross-section of the tower column of the existing bridge tower 7 laterally outwards. The newly added cross-section 8 of the bridge tower expansion and the existing bridge tower 7 are combined into the expanded bridge tower; the connection between the newly added cross-section 8 of the bridge tower expansion and the cross-section of the existing bridge tower 7 is integrated; as Figure 3 shown, after the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower expansion are connected into an integral whole, install a newly added main cable saddle 10 laterally outside the existing main cable saddle 9 at the top of the expanded bridge tower to support the newly added main cable 1 and smooth the alignment of the newly added main cable 1.

[0067] In S2, for the connection between the newly added cross-section 8 of the bridge tower expansion and the cross-section of the existing bridge tower 7, if the existing bridge tower 7 is made of concrete, reinforce bars are implanted in the existing concrete bridge tower and then connected into an integral whole; if the existing bridge tower 7 is made of steel, it is connected into an integral whole with the existing steel structure bridge tower by welding and high-strength bolts.

[0068] S3. Pour the newly added anchor foundation 15: While completing the newly added cross-section 8 of the bridge tower expansion, excavate the foundation pit of the newly added anchor foundation 15 at the side span of the existing suspension bridge, and then pour and form it and set the newly added cable saddle and anchoring system 14 on the newly added anchor foundation 15.

[0069] In the construction steps of S1 - S3 above, on the premise of doing relevant safety measures well, the traffic of the existing suspension bridge can operate normally; however, in the following construction steps, the existing suspension bridge must be closed for construction.

[0070] S4. Erection of the newly added main cable 1: Relying on the expanded bridge tower (the existing bridge tower 7 and the newly added cross-section 8 of the bridge tower expansion), the newly added main cable saddle 10, the newly added anchor foundation 15, the newly added cable saddle and anchoring system 14, and the existing main cable 2, install the construction platform corresponding to the newly added main cable 1 - the catwalk. Install the cable strands of the newly added main cable 1 on the catwalk. After the erection is completed, use a cable compacting machine to compact the cable and install the cable clips. After the main cable erection is completed, carry out the catwalk conversion hoisting, that is, the main cable is erected on the catwalk and adjusted to use the main cable as the load-bearing system and the catwalk is suspended on the main cable.

[0071] In the stage where step S4 is located, as Figure 7 shown, after the installation of the newly added main cable 1 is completed, the newly added main cable 1 only bears its own weight, and the mid-span of the newly added main cable 1 presents as a planar main cable, that is, the lateral positions of the top of the newly added main cable 1 and the mid-span are the same.

[0072] S5. Formation of the spatial cable shape of the newly added main cable 1: As Figure 8 shown, by setting multiple cross braces between the mid-spans of the two newly added main cables 1, gradually adding sections and jacking, the lateral distance between the mid-spans of the two newly added main cables 1 is expanded to the alignment of the expanded completed bridge state; then install the newly added suspension cables 3 at the set distance (at this time, the newly added suspension cables 3 are not tensioned).

[0073] In S5, the cross strut adopts a walking type jacking support device with an arbitrarily variable span within a certain range; it can be understood that the position of the newly added sling 3 needs to be determined according to the position of the existing sling 4 on the existing main cable 2; that is, the longitudinal positions of the newly added sling 3 and the existing sling 4 are arranged at intervals.

[0074] S6. Hoisting and erection of the widened and extended parts on both sides of the stiffening girder: As Figure 9 shown, the widened and extended parts 6 on both sides of the stiffening girder are longitudinally segmented, and a beam transporting machine can be used to transport them from the deck of the existing stiffening girder 5 to the installation position; then, a separated self - walking cable - borne crane supported on the newly added main cable 1 is used for hoisting and positioning, and then temporarily connected to the existing stiffening girder 5 segments. The separated self - walking cable - borne crane gradually moves from the existing bridge tower 7 side to the mid - span, symmetrically hoisting the widened and extended parts 6 on both sides of the stiffening girder. Temporary connections are made between the longitudinally adjacent parts of the widened and extended parts 6 on both sides of the stiffening girder and between them and the existing stiffening girder 5; after the beam segments of the widened and extended parts 6 on both sides of the stiffening girder are hoisted and connected in place, the newly added sling 3 corresponding to the beam segment is tensioned;

[0075] As Figure 10 shown, the separated self - walking cable - borne crane supported on the newly added main cable 1 gradually moves from the bridge tower side to the mid - span side, continuing to hoist the widened and extended parts 6 on both sides of the stiffening girder until the mid - span closure beam segment; a jack is used to push the widened beam segments on both sides at the closure section towards the bridge tower side for positioning, and then the widened and extended parts 6 of the stiffening girder at the mid - span closure section are hoisted and installed, and temporarily connected between the existing stiffening girder 5 and the longitudinally adjacent parts of the widened and extended parts 6 on both sides of the stiffening girder to complete the mid - span closure.

[0076] S7. Adjusting the connection of the widened and extended parts 6 on both sides of the stiffening girder from temporary connection to permanent connection: Fine - tune the elevation at the interfaces between the longitudinally segmented parts of the widened and extended parts 6 on both sides of the stiffening girder and between them and the existing stiffening girder 5 segments, and fine - tune the cable force of the newly added sling 3 to make the beam segment alignment smooth and consistent with the designed alignment of the completed bridge body, and make the cable force of the newly added sling 3 consistent with the designed cable force; and adjust the temporary connections between the longitudinally segmented parts of the widened and extended parts 6 on both sides of the stiffening girder and between them and the existing stiffening girder 5 segments to permanent connections such as welding or high - strength bolt connections, so that the connection between the existing stiffening girder 5 and the widened and extended parts 6 on both sides of the stiffening girder becomes an integral whole. Then, remove the cross struts between the mid - spans of the newly added main cable 1 and the temporary facilities (such as the separated self - walking cable - borne crane) during the transportation and hoisting of the widened and extended parts 6 on both sides of the stiffening girder.

[0077] As Figure 11As shown, the connection between the existing stiffening girder 5 and the widened and extended parts 6 on both sides of the stiffening girder is integrated. After the cable force of the new suspender 3 is tensioned to the cable force of the designed completed bridge suspender, the cross bracing between the mid-spans of the new main cable 1 is removed, and the new main cable 1 maintains the spatial cable shape. The spatial cable shape of the new main cable 1 is formed by the joint constraints of the self-weight of the main cable, the shape of the new suspender 3, and the cable force of the suspender.

[0078] The new suspender 3, as Figure 1 , Figure 2 , Figure 5 shown, is arranged obliquely on the cross-section of the stiffening girder and has a certain inclination angle with the vertical plane; the upper end is connected to the new main cable 1 through a cable clamp, and the lower end is connected to the widened and extended parts 6 on both sides of the stiffening girder through an anchoring device. That is, the widened and extended parts 6 on both sides of the stiffening girder are suspended and supported on the new main cable 1 through the new suspender 3. The new main cable 1 bears the dead and live loads of the widened and extended parts 6 on both sides of the stiffening girder transmitted by the new suspender 3; the mid-span transverse coordinates of the new main cable 1 are located between the transverse coordinates of the tower top and the transverse coordinates of the cable anchoring devices on the widened and extended parts 6 on both sides of the stiffening girder.

[0079] S8. Bridge deck construction: Wind the new main cable 1 with wire ropes for protection; then remove the catwalk; complete the enclosure works such as the top plate and side plates of the new saddle and anchoring system 14 and the tower enclosure of the new main saddle 10 to prevent the relevant steel structures from being eroded by wind and rain; finally, conduct acceptance and open to traffic for operation.

[0080] In this embodiment, by expanding the cross-section of the existing bridge tower 7 and the bridge tower foundation, and adding the new anchor foundation 15, the new saddle and anchoring system 14, and the new main saddle 10, the support for the new main cable 1 and the smooth change of the vertical alignment are realized; then, relying on the existing main cable 2, etc. as the construction platform, the catwalk of the new main cable 1 is erected; after the catwalk erection is completed as the construction platform, the new main cable 1 is erected. It has a small occupied space and is convenient for construction.

[0081] By adding two new main cables horizontally, the overall load-bearing capacity of the suspension bridge is greatly improved. The bridge deck of the existing suspension bridge can be widened as needed, realizing the widening of the suspension bridge in the engineering sense and increasing the bridge deck width; directly widening on both sides of the stiffening girder of the suspension bridge, and smoothly connecting with the connecting lines; by expanding the cross-section of the existing tower column, bearing the vertical force of the new bridge deck and the main cable, the new tower column and foundation occupy less land area, saving land, and at the same time, the corresponding route indicators are high and the driving comfort is good.

[0082] Although the specific implementation manners of the present invention are described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that, based on the technical solutions of the present invention, various modifications or deformations that can be made by those skilled in the art without creative efforts are still within the protection scope of the present invention.

Claims

1. A suspension bridge expansion structure with four main cables in space formed by horizontally adding main cables, which is built based on an existing suspension bridge. The existing suspension bridge includes an existing stiffening girder, existing main cables, existing suspenders, existing main saddles, existing bridge towers, existing anchor foundation, existing saddles for diverging cables and an anchoring system, and is characterized in that Along the length direction of the bridge, on both lateral sides of the existing stiffening girder, widen and expand the two sides of the new stiffening girder and connect them into a whole; the widened and expanded parts on both sides of the stiffening girder are connected to the new main cable through newly added suspenders, and the new main cable is arranged outside the existing main cable; Bridge towers are arranged at both ends of the mid-span of the existing stiffening girder, and main saddles are arranged at the tops of the bridge towers. The main saddles include newly added main saddles and existing main saddles. The new main cable is supported on the newly added main saddle, and the existing main cable is supported on the existing main saddle; The distance between the center of the new main cable and the bridge axis gradually increases from the top of the tower to the mid-span, and the lateral distance from the mid-span to the bridge axis is the largest; the newly added suspenders and the existing suspenders are arranged longitudinally at intervals.

2. The suspension bridge expansion structure with a new main cable added horizontally to form a spatial four-main-cable as claimed in claim 1, wherein The newly added main saddle and the existing main saddle are arranged side by side, and the newly added main saddle is located laterally outside the existing main saddle; the elevations of the new main cable and the existing main cable at the top of the tower are the same.

3. The suspension bridge expansion structure with a new main cable added horizontally to form a spatial four-main-cable as described in claim 1, characterized in that The elevation of the mid-span of the new main cable is higher than that of the mid-span of the existing main cable by a set distance; the two new main cables or the two existing main cables are arranged symmetrically laterally with respect to the bridge axis.

4. The suspension bridge expansion structure with four main cables in space formed by horizontally adding new main cables as described in claim 1, characterized in that The bridge tower is divided into an existing bridge tower and a newly added cross-section for bridge tower expansion. The newly added cross-section for bridge tower expansion is arranged longitudinally and laterally outside the existing bridge tower. The newly added main saddle is arranged on the top surface of the newly added cross-section, and the existing main saddle is arranged on the top surface of the existing bridge tower.

5. The suspension bridge expansion structure with a horizontally newly added main cable to form a spatial four-main-cable as described in claim 1, characterized in that, The distance between the centers of the saddle grooves of the newly added main saddle and the existing main saddle is controlled according to twice the diameter of the new main cable. The saddle groove shape of the newly added main saddle is arranged at an oblique angle with the vertical plane, which is the same as the oblique angle of the mid-span of the new main cable with the vertical plane.

6. The suspension bridge expansion structure with a laterally newly added main cable to form a spatial four-main-cable as described in claim 1, characterized in that, On both sides of the side spans of the existing suspension bridge, two existing anchor foundation are respectively arranged. An existing cable saddle and an anchoring system are arranged on the existing anchor foundation. The two ends of the two existing main cables are respectively connected to the existing cable saddle and the anchoring system; a newly added cable saddle, an anchoring system and a newly added anchor foundation are also arranged to anchor the two ends of the new main cable.

7. The suspension bridge expansion structure with four main cables in space formed by horizontally adding new main cables as described in claim 1, characterized in that The newly added anchor foundation and the existing anchor foundation are arranged separately before and after, and the newly added anchor foundation is adapted to the angle of the new main cable. At the same time, it avoids the connection structures of the side spans of the suspension bridge and is arranged laterally outside the existing anchor foundation.

8. The suspension bridge expansion structure with four main cables in space formed by horizontally adding new main cables as described in claim 1, wherein The existing stiffening girder can adopt a box girder, a truss girder or a slab girder. The widened and expanded parts on both sides of the stiffening girder are connected to the existing stiffening girder by welding or bolts; anchoring devices are arranged on both sides of the widened and expanded parts on both sides of the stiffening girder. One end of the newly added suspender is connected to the new main cable, and the other end is connected to the anchoring device.

9. The expansion method of the expansion structure of the suspension bridge with four main cables formed by horizontally adding main cables as described in any one of claims 1-8, characterized in that, Including the following steps: S1. New bored cast-in-place pile foundations and new bearing platforms are added laterally outside the existing bridge tower foundation; S2. On the basis of the new bearing platform, expand the newly added cross-section of the bridge tower and install the newly added main saddle; S3. Pour the newly added anchor foundation, and set up the newly added cable saddle and the anchoring system; then the construction is closed; S4. Relying on the existing bridge tower and the existing main cable, install the catwalk of the new main cable and erect the new main cable; after erection, the mid-span of the new main cable presents a planar main cable under its own weight; S5. Use multiple cross braces between the mid-spans of the two new main cables. By gradually adding sections and jacking, the space between the mid-spans of the two new main cables is opened to reach the state of the spatial cable after the bridge is widened; install the newly added suspenders at a set distance, and at this time the newly added suspenders are not tensioned; S6. The widened and expanded parts on both sides of the stiffening beam are divided into longitudinal sections and hoisted and installed in place by a separate self-propelled cable-carrying crane supported on the newly added main cable until the middle span is closed; temporary connections are used between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and between the beam sections of the existing stiffening beams; S7. Slightly adjust the elevation of the interface between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and the existing stiffening beam sections, as well as the cable force of the newly added slings, and then adjust the temporary connection between the longitudinal beam sections of the widened and expanded parts on both sides of the stiffening beam and the existing stiffening beam sections to a permanent connection by welding or high-strength bolt connection; then remove the temporary facilities for the transportation and installation of the cross braces and beam sections; S8. Wrap the newly added main cable with wire for protection; then dismantle the catwalk; complete the sealing project of the newly added loose cable saddle and anchoring system and the newly added main cable saddle; finally, carry out acceptance and open to traffic operation.

10. The expansion method of the suspension bridge expansion structure with four main cables in space formed by horizontally adding new main cables as described in claim 9, characterized in that, In S6, the beam transporting machine transports the widened and expanded beam sections on both sides of the stiffening beam from the existing stiffening beam bridge deck to the desired location; after the widened and expanded beam sections on both sides of the stiffening beam are installed in place, the newly added slings corresponding to the widened and expanded beam sections on both sides of the stiffening beam are tensioned.

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